JP6891682B2 - Electrical steel sheet and its manufacturing method, rotor motor core and its manufacturing method, stator motor core and its manufacturing method, and motor core manufacturing method - Google Patents

Description

The present invention is suitable for applications such as magnetic cores of motors, generators, and transformers, and an electromagnetic steel sheet having an increased magnetic flux density that can contribute to miniaturization and high efficiency of these magnetic cores, a method for manufacturing the same, and the electromagnetic steel. The present invention relates to a motor core using a steel plate and a method for manufacturing the same.

Motors and generators are required to have high efficiency as a measure against global warming. Therefore, electrical steel sheets used for magnetic cores of motors, generators, etc. are required to have high magnetic flux density and low iron loss, and particularly, low iron loss in a high frequency region is strongly required.
Further, in recent years, with the development of motor drive systems, it has become possible to control the frequency of a drive power source, and the number of motors that perform variable speed operation or high-speed rotation at a commercial frequency or higher is increasing. In such a motor that rotates at high speed, the centrifugal force acting on a rotating body such as a rotor increases in proportion to the radius of gyration and the square of the rotation speed. A high-strength material is required as the material. Further, since the rotor is premised on repeating rotation and stopping frequently, the material for the rotor is required to have excellent fatigue strength. High-strength materials are also advantageous in this respect.

The electromagnetic steel sheet usually contains Si, and it is known that Mn, Al, and the like are further added for various purposes.
Patent Document 1 discloses a specific non-oriented electrical steel sheet containing Si, Mn, and Al in specific quantities as non-oriented electrical steel sheets having low iron loss and high hardness. According to Patent Document 1, by controlling the content ratio of Si and Al and the ductility of the hot-rolled sheet annealed plate, a non-oriented electrical steel sheet that achieves both reduction of high-frequency iron loss and steel sheet productivity can be obtained. It is said that it will be done.

Further, Patent Document 2 describes a specific non-oriented electrical steel sheet containing Si, Mn, Al and P in specific amounts as non-oriented electrical steel sheets having a high magnetic flux density and excellent iron loss characteristics in a high frequency region. Electrical steel sheets are disclosed. According to Patent Document 2, increasing the amount of phosphorus present on the grain boundaries is effective in suppressing a decrease in magnetic flux density and reducing iron loss.

Further, conventionally, electrical steel sheets may be used after additional heat treatment. "Strain removal annealing" is known as a typical example. This is a heat treatment for finally removing unnecessary strain because the strain unavoidably introduced into the steel plate due to punching or the like when processing the steel plate as an electric part worsens the iron loss. It is applied to cut out blanks or laminated cores. However, in strain relief annealing, although the effect of releasing strain and improving iron loss is clear, it is particularly high because the crystal orientation unfavorable for magnetic characteristics may develop and the magnetic flux density may decrease. When magnetic characteristics are required, it is required to avoid a decrease in magnetic flux density due to strain relief annealing.
Although this problem is not directly solved, as a process similar to strain relief annealing, the steel sheet after finish annealing is intentionally re-cooled and shipped in the cold-rolled state, and the cold-rolled steel sheet is shipped. A so-called "semi-processed material" has been developed in which a steel sheet user performs annealing to obtain the required magnetic properties after forming an iron core by processing the material, and is disclosed in, for example, Patent Documents 3 and 4.

Japanese Unexamined Patent Publication No. 2007-2407047 Japanese Unexamined Patent Publication No. 2015-40309 Japanese Unexamined Patent Publication No. 3-223424 International Publication No. 2014/129034

It is assumed that the deterioration of characteristics due to the above-mentioned strain removing annealing becomes a big problem. For example, there is a case where blanks for a rotor and a stator of a motor are cut out from the same steel plate and used. This is because the blank cut out for the stator has a large part in the center as a space, so if the material of this part is used as the blank for the rotor, it is very advantageous in terms of material yield, and such a situation is common. It can be said that. At this time, strength is required for the material cut out for the rotor, but strength is not required for the material cut out for the stator, and high magnetic flux density and low iron loss are required as with ordinary recrystallized materials. Will be done. Therefore, the blank cut out for the stator is molded into the stator core and then subjected to additional heat treatment to be sufficiently recrystallized. At this time, the high-strength material utilizing the precipitates and the microstructure refinement has a large structural change, that is, a material change in the additional heat treatment, but not only the strength is lowered, but also the magnetic characteristics, particularly the high-frequency characteristics, are normal. It was inferior to the recrystallized material and could only be obtained.

The present invention has been made in view of the above circumstances, and uses an electromagnetic steel sheet having excellent fatigue strength, low iron loss, and suppressed decrease in magnetic flux density during strain removing annealing, a method for producing the same, and the electrical steel sheet. Provided are a motor core having a low iron loss and a high magnetic flux density and a method for manufacturing the same.

As a result of diligent studies, the present inventors have found that in an electromagnetic steel sheet containing a relatively large amount of Mn, in the initial stage of recrystallization structure formation from recovery to the initial stage of grain growth, the heating rate is increased to advance the process. In the later stages of recrystallization structure formation such as recrystallization to late grain growth, it was found that when these were advanced by slow heating at a low heating rate, the reduction in magnetic flux density due to the subsequent heat treatment was suppressed, and further fatigue was found. It was confirmed that the strength was also good, and the present invention was completed.

That is, in the electromagnetic steel plate according to the present invention, Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0 % by mass or less, and Ca, Mg, Ce, Ti, A total of one or more elements selected from Ba and Be is 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is 0. A steel plate consisting of less than .002% by mass , the balance Fe and unavoidable impurities.
The average crystal grain size is 60 μm or more and 80 μm or less .
The steel sheet has an oxide containing Si and Mn, the average diameter of the oxide is 112 nm or more, and the number density of the oxide contained in the steel sheet is 0.3 × 10 ^{4 to} 6.6 ×. characterized in that it is a 10 ⁵ / mm ^2.

In the present invention, it is preferable that the average composition of the oxide contains Si in an amount of 15% by mass or more and 70% by mass or less and Mn in an amount of 20% by mass or more and 60% by mass or less.

In the steel sheet of the present invention, the average diameter of the oxide is preferably 250 nm or more.

In the steel sheet of the present invention, the number density of the oxide contained in the steel sheet is preferably 2.0 × 10 ^{4 to} 1.2 × 10 ⁵ pieces / mm ² .

In the steel sheet of the present invention, the magnetic flux density before performing the heat treatment under the conditions of a heating rate of 100 ° C./h or less, a maximum reaching temperature of 750 ° C. to 850 ° C., and a holding time of 750 ° C. or more for 0.5 hours or more and 100 hours or less. BB / BA ≧ 0.98, where BB and the magnetic flux density after the implementation are BB.

In the present invention, it is preferable that the steel sheet is an α-γ transformation system and the ratio of {100} <011> orientation to random strength at the position of 1/2 thickness of the steel sheet is 50 or more.

In the method for producing an electromagnetic steel sheet of the present invention, Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0 % by mass or less, and Ca, Mg, Ce, Ti, A total of one or more elements selected from Ba and Be is 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is 0. A hot rolling step using an ingot consisting of less than .002% by mass , the balance Fe and unavoidable impurities as a hot-rolled plate, a step of pickling the hot-rolled plate, and a cold rolling using the hot-rolled plate as a cold-rolled plate. It has a step and a finish annealing step of the cold-rolled plate.
The heating conditions of the finish annealing step are an average heating rate of 5 ° C./s or more from 400 ° C. to 750 ° C., a maximum reaching temperature of 750 ° C. or more and less than 1000 ° C., and a holding time of 45 seconds or more and 150 seconds or less at 750 ° C. or more. It is characterized by being.

The method for producing an electromagnetic steel sheet which is an α-γ transformation system of the present invention is an α-γ transformation system, in which Si is 2.0% by mass or more and 4.5% by mass or less and Mn is 2.5% by mass or more. 0 % by mass or less, and one or more elements selected from Ca, Mg, Ce, Ti, Ba, and Be in total of 0.0001% by mass or more and 0.10 % by mass or less , and Al is 0.03% by mass. %, C is less than 0.002% by mass, S is less than 0.002% by mass , a hot rolling step of using an ingot composed of the balance Fe and unavoidable impurities as a hot-rolled plate, and a step of pickling the hot-rolled plate. A cold rolling step of using the hot rolled plate as a cold rolled plate and a finishing annealing step of the cold rolled plate are provided.
The heating conditions of the finish annealing step are an average heating rate of 5 ° C./s or more from 400 ° C. to 750 ° C., a maximum ultimate temperature of 750 ° C. or more and less than 1000 ° C., and heat when the ingot is heated from the α phase single phase. The expansion behavior is characterized in that the holding time at a temperature of T1 or less and 750 ° C. or more, which is defined as a turning point deviating from the linear expansion behavior in a direction in which the inclination becomes smaller, is 20 seconds or more and 150 seconds or less.

The rotor motor core of the present invention is characterized in that the electromagnetic steel sheets of the present invention are laminated.

The method for manufacturing a motor core for a rotor of the present invention is characterized by having a step (I) of obtaining a steel sheet blank by punching an electromagnetic steel sheet and an electromagnetic steel sheet, and a step (II) of laminating the steel sheet blanks. ..

In the motor core for a stator of the present invention, Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0 % by mass or less, and Ca, Mg, Ce, Ti, Ba, etc. In total, one or more elements selected from Be and Be are 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is 0.002. A steel plate consisting of less than mass% , balance Fe and unavoidable impurities , having an average crystal particle size of more than 80 μm and 150 μm or less, the steel plate has an oxide containing Si and Mn, and the average diameter of the oxide is It is characterized in that electromagnetic steel plates having a mass of 112 nm or more and a number density of the oxides contained in the steel plate of 0.3 × 10 ^{4 to 6.6 × 10 5} pieces / mm ^{2 are laminated.}

The stator motor core of the present invention preferably contains Si in an average composition of 15% by mass or more and 70% by mass or less and Mn in an amount of 20% by mass or more and 60% by mass or less.

The method for manufacturing a motor core for a stator of the present invention includes a step (I') of obtaining a steel sheet blank by punching the electromagnetic steel sheet of the present invention, and a step (II') of laminating the steel sheet blank. After the step (I') and before or after the step (II'), the steel sheet blank has a heating rate of 100 ° C./h or less and a maximum reaching temperature of 750 ° C. to 850 ° C., 750 ° C. or higher. It is characterized by having a step (III') of making the average crystal grain size of the steel sheet more than 80 μm and 150 μm or less by performing the heat treatment under the condition that the holding time is 0.5 hours or more and 100 hours or less.

The method for manufacturing a motor core of the present invention is a method for manufacturing a motor core for a rotor and a motor core having the motor core for a stator, wherein the steel plate blank of the motor core for the rotor and the steel plate blank of the motor core for the stator are the same. It is characterized by being punched from the electromagnetic steel sheet of the present invention.

According to the present invention, an electromagnetic steel sheet having excellent fatigue strength, low iron loss, and suppressing a decrease in magnetic flux density during strain resilience annealing and a method for manufacturing the same, and a low iron loss using the electromagnetic steel sheet, high. A motor core having a magnetic flux density and a method for manufacturing the same can be provided.

FIG. 1 is a schematic schematic process diagram showing an example of a method for manufacturing a motor core. FIG. 2 is a diagram showing a processed structure formed on the surface layer of a rolled plate. FIG. 3 is a graph showing the thermal expansion / contraction behavior measured when the steel sheet is heated from the α-phase single-phase state.

Hereinafter, the electromagnetic steel sheet according to the present invention and its manufacturing method, and the motor core according to the present invention using the electromagnetic steel sheet and its manufacturing method will be described in detail in order.
It should be noted that the terms such as "parallel", "vertical", and "same" and the values of length and angle used in the present specification to specify the shape and geometric conditions and their degrees are strict. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.
Further, in the present invention, "ppm" represents a mass ratio unless otherwise specified.

[Electromagnetic steel sheet]
The electrical steel sheet of the present invention has a low iron loss, a decrease in magnetic flux density during strain relief annealing is suppressed, and a final product can be manufactured while maintaining a high magnetic flux density.
The electromagnetic steel plate according to the present invention contains Si in an amount of 2.0% by mass or more and 4.5% by mass or less, Mn in an amount of 2.5% by mass or more and 5.0% by mass or less, and Ca, Mg, Ce, Ti, Ba, etc. And Be contains one or more elements selected from Be in total of 0.0001% by mass or more and 0.1% by mass or less, Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is 0. A steel plate containing less than .002% by mass and containing Fe as a main component.
The average crystal grain size is 60 μm or more and 80 μm or less.

The steel sheet has a relatively high concentration of Mn, and as a result of suppressing the Al content, low iron loss is achieved, and a decrease in magnetic flux density during strain removal annealing is suppressed as compared with the conventional case. Further, by setting the average crystal grain size of the electrical steel sheet to 60 μm or more and 80 μm or less, the decrease in magnetic flux density at the time of strain removal annealing is further suppressed.

That is, the electromagnetic steel sheet of the present invention has the following features.
The above-mentioned electrical steel sheet has excellent fatigue strength, low iron loss, and is suitable for rotor motor core applications. Therefore, the electromagnetic steel sheet can be punched into a desired rotor shape, and the obtained steel sheet blanks are laminated to produce a suitable motor core for a rotor.
Further, by strain-removing and annealing the electromagnetic steel sheet, an electromagnetic steel sheet having a low iron loss and a high magnetic flux density can be obtained. The electrical steel sheet after strain removal and annealing is suitable for use as a motor core for a stator. Therefore, a suitable motor core for a stator can be manufactured by punching the electromagnetic steel sheet of the present invention into a desired stator shape and performing strain relief annealing on the obtained steel sheet blank before or after laminating. it can.
Further, from the electromagnetic steel sheet of the present invention, a steel sheet blank for a rotor core and a steel sheet blank for a stator are punched out, and only the steel sheet blank for a stator is distorted and annealed to obtain a suitable motor core for a rotor and a suitable motor core for a stator. , It is also possible to manufacture from the same electromagnetic steel sheet at once. Therefore, it is possible to more efficiently utilize one electrical steel sheet to manufacture a motor core having excellent fatigue strength, low iron loss, and suppressed decrease in magnetic flux density during strain relief annealing.
Hereinafter, preferred forms of such electrical steel sheets of the present invention will be described in more detail.

<Oxide>
The electromagnetic steel sheet of the present invention further has an oxide, and the average composition of the oxide preferably contains Si in an amount of 15% by mass or more and 70% by mass or less and Mn in an amount of 20% by mass or more and 60% by mass or less. The oxide has the effect of controlling the growth of Fe crystal grains, which are the parent phase, with orientation selectivity by dispersing as pinning particles in the steel plate, and its composition is consistent with the Fe crystal, which is the mother phase. It is considered that the above-mentioned pinning effect is influenced by the above, and when the average composition is out of this range, this effect becomes small. The composition of the oxide can be determined by analyzing a sample prepared by the extraction replica method at a depth of 1/4 t with respect to the thickness t from the surface of the electromagnetic steel sheet by an energy dispersive X-ray analyzer (EDX). Since the composition varies with individual oxides, the composition of the individual oxides for at least 20 oxides is determined and averaged. That is, the contribution to the average composition is the same regardless of whether it is a large oxide or a small oxide, and the size (the amount of elements forming the oxide) does not matter. In addition, although each element may be segregated in the oxide, the integrated oxide shall be measured as one oxide.
Further, the electromagnetic steel sheet of the present invention preferably has an oxide average diameter of 250 nm or more. In the present invention, the oxide promotes the selective grain growth of crystal grains having a crystal orientation favorable to the magnetic properties under specific conditions as described later, and the selective grains of the crystal grains having a disadvantageous crystal orientation. It is considered that the effect of suppressing growth is exerted through the pinning effect, but oxides having a small size have a small contribution to the orientation selection effect, and when the average diameter is out of this range, the effect of invention becomes small.
The average diameter of the oxides is determined by observing at least 100 oxides from a sample prepared by the extraction replica method at a depth of 1/4 t with respect to the thickness t from the surface of the electromagnetic steel plate with a transmission electron microscope. Find and average it. For oxides whose observation form is not substantially circular but has a stretched shape, the size shall be calculated with the observation area of each oxide as the diameter equivalent to a circle. This calculation can be easily performed by image processing or the like.
The number density of oxides is determined by measuring oxides in a field of view of 10 μm × 10 μm using the same sample and averaging the measured values of at least 5 fields of view.
Further, the electromagnetic steel sheet of the present invention preferably has a number density of the oxides contained in the steel sheet of 2.0 × 10 ^{4 to} 1.2 × 10 ⁵ pieces / mm ² . In the present invention, the oxide promotes the selective grain growth of crystal grains having a crystal orientation favorable to the magnetic properties under specific conditions as described later, and the selective grains of the crystal grains having a disadvantageous crystal orientation. Since it is thought that the effect of suppressing growth is exerted through the pinning effect, this effect cannot be expected if it does not exist at all. Further, if the number density is too high, the effect of inhibiting grain growth or domain wall movement is increased and not only the magnetic characteristics are deteriorated, but also the fatigue characteristics are deteriorated because the oxide becomes the starting point of fatigue failure.
By appropriately controlling the morphology including the composition of the oxide containing Si and Mn in high concentrations, the effect of suppressing the decrease in magnetic flux density at the time of strain removal annealing can be obtained more remarkably.

That is, the electromagnetic steel sheet of the present invention can suppress the decrease in magnetic flux density that occurs during the growth of recrystallized grains. For example, the heating rate is 100 ° C./h or less, and the maximum ultimate temperature is 750 ° C. to When the magnetic flux density before the heat treatment is BB and the magnetic flux density after the heat treatment is BA under the conditions that the holding time at 850 ° C. and 750 ° C. or higher is 0.5 hours or more and 100 hours or less.
BA / BB ≧ 0.98
Relationship can be achieved.
The reason for this is not always clear, but I think it is as follows.
In conventional electrical steel sheets, when additional heating such as strain removal annealing is performed, other orientations that are more favorable for magnetic characteristics than crystal grains having {100} or {411} orientations that are considered to be good for magnetic characteristics. It is presumed that the growth of crystal grains having ({111} or {211}) becomes dominant and the magnetic flux density is greatly reduced. The electromagnetic steel sheet of the present invention has a relatively high concentration of Mn and a small amount of Al, so that the crystal orientation at the time of manufacturing the electromagnetic steel sheet (that is, after finish annealing and before strain relief annealing) is advantageous for increasing the magnetic flux density. That is, it is presumed that the crystal grains having the {100} or {411} orientation are dominant. In the electromagnetic steel sheet of the present invention, {100} <011> is predominantly present after finish annealing, and since it has relatively fine crystal grains, the orientation difference between adjacent grains is small, and the gradual heating grain growth after additional heating. It is presumed that the high magnetic flux density is maintained even in the orientation development of time without the growth of other orientations becoming dominant.
In addition to this, as a result of having a relatively high concentration of Mn, suppressing the Al content, and further containing one or more elements selected from Ca, Mg, Ce, Ti, Ba, and Be. In particular, the oxide morphology has changed, which promotes the selective growth of crystal grains having a crystal orientation advantageous for magnetic properties as pinning particles in the selective growth of a specific orientation during grain growth by slow heating, or It may have a favorable effect on the selective growth suppression of crystal grains having a crystal orientation that is disadvantageous to the magnetic properties. That is, in the steel of the present invention in which the oxide morphology is appropriately controlled, crystals generated at a relatively high heating rate in the initial stage of recrystallization (stages having a crystal grain size of 80 μm or less) are produced in the latter stage of recrystallization. It is considered that the orientation selectivity is changed when the growth proceeds at a relatively low heating rate in the grain growth stage (the stage where the crystal grain size exceeds 80 μm).
It should be noted that the number of oxides in the steel of the present invention is not so large, and it is unclear whether or not this has a sufficient effect as the pinning particles as described above, and it should be noted that this is just one interpretation.

Further, by adopting the above-mentioned crystal grain size and oxide form, the fatigue strength is also very good. It is generally known that grain refinement is effective for fatigue strength, and it is known that coarse oxides are the starting point of fatigue fracture, which are not particularly mentioned. In the high Mn-based material, good fatigue characteristics in the material in which the crystal grain size and the oxide morphology are preferably controlled in order to avoid deterioration of the magnetic properties during strain relief annealing are also one of the features of the steel of the present invention. ..

The electromagnetic steel sheet of the present invention is composed of at least a steel sheet, and may further have an insulating film or the like, if necessary. Hereinafter, each configuration of the electromagnetic steel sheet according to the present invention will be described in detail.

<Sheet steel composition>
In the electromagnetic steel plate of the present invention, the steel plate contains Si in an amount of 2.0% by mass or more and 4.5% by mass or less, Mn in an amount of 2.5% by mass or more and 5.0% by mass or less, and Ca, Mg, Ce, Ti. A total of 0.0001% by mass or more and 0.1% by mass or less of one or more elements selected from Ba and Be is contained, Al is less than 0.03% by mass, C is less than 0.002% by mass, and S. Is less than 0.002% by mass and has a chemical composition containing Fe as a main component.
In the present invention, the main component means a component showing the highest ratio, and usually has an element content of 50% by mass or more.

The chemical composition is the composition of the steel components constituting the steel sheet. If the steel sheet used as the measurement sample has an insulating film or the like on its surface, it is necessary to remove it before measurement.
Examples of the method for removing the insulating film of the electromagnetic steel sheet are as follows. First, the electromagnetic steel sheet having an insulating coating or the like, NaOH: _10% by mass ₊ H 2 O: 90 wt% aqueous sodium hydroxide for 15 minutes at 80 ° C., immersion. Then, _{it is immersed in a sulfuric acid aqueous solution of H 2} SO ₄ : 10% by mass + H ₂ O: 90% by mass at 80 ° C. for 3 minutes. Thereafter, _HNO 3: 10 _{wt% +} H 2 O: by the 90 wt% nitric acid aqueous solution, 1 minute weak at room temperature, washed immersed in. Finally, dry with a warm air blower for a little less than 1 minute. As a result, a steel sheet from which the insulating film described later has been removed can be obtained.

(Si: 2.0% by mass or more and 4.5% by mass or less)
In the electromagnetic steel sheet of the present invention, the Si content is 2.0% by mass or more and 4.5% by mass or less. In non-oriented electrical steel sheets, Si is generally added to reduce iron loss by increasing the electrical resistance of the steel sheet. If the Si content is less than 2.0% by mass, not only good magnetic properties cannot be ensured, but also it becomes difficult to keep the oxide morphology in an appropriate range. On the other hand, if it exceeds 4.5% by mass, it becomes difficult to keep the composition of the oxide in an appropriate range.

(Mn: 2.5% by mass or more and 5.0% by mass or less)
In the electromagnetic steel sheet of the present invention, the content ratio of Mn is 2.5% by mass or more and 5.0% by mass or less. In non-oriented electrical steel sheets, Mn is generally added to reduce iron loss by increasing the electrical resistance of the steel sheet. If the Mn content is less than 2.5% by mass, not only good magnetic properties cannot be ensured, but also it becomes difficult to maintain the form of the oxide in an appropriate range. On the other hand, if it exceeds 5.0% by mass, it becomes difficult to keep the composition of the oxide in an appropriate range.
Further, if the Mn concentration is within this range, the magnetic flux density can be increased by assuming that the crystal orientations of the steel sheets are strongly integrated in the {100} <011> orientations by the manufacturing method described later.
It is preferably 3.1% or more, more preferably 3.6% or more, still more preferably 4.1% or more.

(Ca, Mg, Ce, Ti, Ba, Be: total 0.0001% by mass or more and 0.1% by mass or less)
The electromagnetic steel sheet of the present invention contains 0.0001% by mass or more and 0.1% by mass or less in total of one or more elements selected from Ca, Mg, Ce, Ti, Ba, and Be. By containing 0.0001% by mass or more of these elements in total, the effect of orientation selectivity at the time of strain removal annealing is enhanced. It is considered that this is because these elements are contained in combination with the oxide containing Si and Mn, which is the subject of the present invention. On the other hand, even if it is added excessively, not only the effect of the invention is saturated, but also precipitates other than oxides are formed, which hinders the movement of the domain wall and inhibits the grain growth, which may deteriorate the iron loss. The upper limit is 0.1% by mass.

(Al: less than 0.03% by mass)
In the present invention, Al is an element to be avoided. Al is a strong oxide-forming element, and if Al is contained in a high concentration, it becomes difficult to form an oxide having a preferable form, particularly a preferable composition, for the effect of the present invention. Therefore, it is set to less than 0.03% by mass. It is preferably less than 0.02% by mass, more preferably less than 0.01% by mass. It also contributes to improving fatigue characteristics by avoiding the formation of coarse and hard oxides.

(C: less than 0.002% by mass)
C may form carbides and deteriorate the magnetic properties in a high magnetic field. Further, when magnetic aging occurs, the magnetic characteristics in a high magnetic field also deteriorate, so it is preferable to lower the C content. Therefore, the C content is less than 0.002% by mass.
From the viewpoint of manufacturing cost, it is advantageous to reduce the C content by degassing equipment (for example, RH vacuum degassing equipment) at the molten steel stage, and if the C content is less than 0.002% by mass, the magnetic aging is suppressed. The effect is great. Since the electromagnetic steel sheet according to the present invention does not use non-metal precipitates such as carbides as the main means for increasing the strength, there is no merit of intentionally containing C, and it is preferable that the C content is low. Therefore, the C content is preferably 0.0015% by mass or less, and more preferably 0.0012% by mass or less. By using a technique such as electrodeposition, it is possible to reduce the content to 0.0001% by mass or less, which is below the limit of chemical analysis, and the C content may be 0%. On the other hand, considering the industrial cost, the lower limit is 0.0003%.

(S: less than 0.002% by mass)
Since S may form sulfides and deteriorate the magnetic properties in a high magnetic field, the S content is preferably low. The S content is less than 0.002% by mass, more preferably 0.0004% by mass or less, even more preferably 0.0002% by mass or less, and most preferably 0.0001% by mass or less. .. The S content may be 0% by mass.

In the electromagnetic steel sheet of the present invention, the steel sheet may further contain other elements as long as the effects of the present invention are not impaired. Examples of the elements that may be contained include Sn, Sb, N, P, Cr, Ni, Cu, B, Nb, Mo, rare earth elements (REM) and the like. Hereinafter, these elements, which have a relatively strong influence on the effects of the present invention, will be described.

(Sn + Sb: 0.005% by mass or more and 0.1% by mass or less)
Both Sn and Sb have the effect of improving the texture of non-oriented electrical steel sheets and enhancing the magnetic properties, but in order to obtain this effect, one or more of Sb and Sn must be 0.005% by mass or more in total. Need to be added. On the other hand, if it is added excessively, the steel becomes brittle and plate breakage and hesitation during steel sheet production increase. Therefore, it is preferable that one or more of Sb and Sn are 0.1% by mass or less in total.

(N: 0.0040% by mass or less)
Like C, N deteriorates the magnetic properties in a high magnetic field due to the formation of nitrides and magnetic aging. Therefore, the N content is preferably 0.0040% by mass or less. The N content is preferably low in order to avoid deterioration of the magnetic properties in a high magnetic field, and if it is 0.0027% by mass or less, the adverse effects on the magnetic properties in a high magnetic field due to magnetic aging and the formation of nitrides are sufficiently avoided. it can. The N content is even more preferably 0.0022% by mass or less, and even more preferably 0.0015% by mass or less. By using a technique such as electrodeposition, it is possible to reduce the content to 0.0001% by mass or less, which is below the limit of chemical analysis, and the N content may be 0% by mass. On the other hand, considering the industrial cost, the lower limit is 0.0003% by mass.

(P: 0.5% by mass or less)
The content of P is controlled for the purpose of adjusting the strength, nitriding during production, and suppressing carburizing, and further, when segregated at the grain boundaries before cold rolling, the texture is improved and the magnetic flux density is improved. It is known that it can be contained in an amount of 0.001% by mass or more. In a general practical steelmaking method, impurities may be contained in an amount of about 0.002% by mass or more. On the other hand, excessive addition makes the steel embrittlement and lowers cold ductility and workability of the product. Therefore, the P content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less. Is.

(Cr: 20% by mass or less)
The content of Cr is controlled for the purpose of adjusting strength, corrosion resistance, and controlling oxidation behavior during manufacturing, and it is known that it particularly improves high-frequency characteristics, and it is possible to contain Cr in an amount of 0.001% by mass or more. Is. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.01% by mass or more. On the other hand, excessive addition increases the addition cost and lowers the magnetic properties, so the Cr content is preferably 20% by mass or less, and more preferably 5% by mass or less.

(Ni: 10% by mass or less)
The content of Ni is controlled for the purpose of adjusting strength, corrosion resistance, and controlling oxidation behavior during manufacturing, and it is also known to improve high-frequency characteristics in particular, and it is possible to contain Ni in an amount of 0.001% by mass or more. Is. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.01% by mass or more. On the other hand, excessive addition increases the addition cost and lowers the magnetic properties, so the Ni content is preferably 10% by mass or less, more preferably 3% by mass or less.

(Cu: 0.2% by mass or less)
Cu, as a solid solution element, significantly reduces the saturation magnetic flux density Bs of the steel sheet. A decrease in the saturation magnetic flux density Bs leads to a decrease in magnetic characteristics. Therefore, it is not necessary to intentionally contain Cu in the steel sheet of the electromagnetic steel sheet according to the present invention unless there is a special purpose. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.01% by mass or more. Therefore, the Cu content is preferably 0.2% by mass or less, and more preferably 0.15% by mass or less. On the other hand, it is also known that the strength can be increased by Cu precipitation, and the electromagnetic steel sheet according to the present invention can be appropriately used according to a known technique.

(B: 0.01% by mass or less)
It is known that the content of B is controlled for the purpose of suppressing nitriding and carburizing during production, and in particular, it forms a composite oxide containing oxides and nitrides to improve magnetic properties. It can be contained in an amount of 0.0001% by mass or more. On the other hand, excessive addition makes the steel brittle and lowers the magnetic properties. Therefore, the B content is preferably 0.01% by mass or less, and more preferably 0.005% by mass or less.

(Nb: 0.0020% by mass or less)
Nb does not need to be intentionally contained because precipitates such as NbC effectively increase the strength, but these precipitates hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field. Therefore, the Nb content is preferably 0.0020% by mass or less, and more preferably 0.0010% by mass or less. In a practical steelmaking method in which scrap or the like is mixed, impurities may be contained in an amount of about 0.0002% by mass or more.

(Mo: 0.0020% by mass or less)
It is known that the content of Mo is controlled for the purpose of suppressing nitriding and carburizing during production, and in particular, it forms a composite oxide containing oxides and carbides to improve magnetic properties. It can be contained in an amount of .0001% by mass or more. On the other hand, since these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field, the Mo content is preferably 0.0020% by mass or less, and more preferably 0. It is 0015 mass% or less.

(REM: 0.050% by mass or less)
REM is known to form a composite oxide containing an oxide and a sulfide to improve magnetic properties, and can contain 0.0001% by mass or more. On the other hand, these precipitates may hinder the movement of the domain wall and significantly deteriorate the magnetic properties in a high magnetic field. Therefore, the REM content is preferably 0.050% by mass or less, preferably 0.010. It is less than mass%.

Further, in the present invention, the mother steel sheet preferably has a chemical composition satisfying the α-γ transformation system. The α-γ transformation system refers to a component system having T1 and T2 in the thermal expansion / contraction behavior described later. Since the base steel sheet has a chemical composition that satisfies the α-γ transformation system, an excellent directional electromagnetic steel sheet having a {100} <011> orientation to random strength ratio of 50 or more at the position of 1/2 thickness of the steel sheet can be obtained. It becomes possible to manufacture.
Further, since the crystal grains in the {100} <011> orientation become more dominant when the steel sheet satisfies the α-γ transformation system, the orientation development during the slow heating grain growth after the additional heating also has other orientations. It favors the maintenance of high magnetic flux density without the predominance of growth.

In the present invention, the thermal expansion / contraction behavior when the steel sheet is heated from the α-phase single-phase state is measured and graphed as shown in FIG. ℃) is determined.
Specifically, T1 is a point deviating from the linear expansion behavior of the α-phase single-phase in the direction in which the slope becomes smaller. This indicates that the α phase, which has a relatively large occupied volume per Fe atom, is transformed into the γ phase, which has a relatively small occupied volume, resulting in volume contraction.
This thermal expansion / contraction behavior becomes steeper again as the temperature is further increased. Then, it begins to show monotonous expansion behavior again. At this time, the point where the slope becomes zero is defined as T2. This indicates that a considerable amount of the γ phase is formed in the α phase, and the thermal expansion behavior in the two phases of α + γ or the single phase of γ is exhibited. When the number of γ phases formed is small, the thermal expansion / contraction curve shows an inflection point but does not have a region where the slope becomes negative and continues to increase monotonically. T2 cannot be determined in this situation. Such steels are not included in the α-γ transformation system specified in the present invention because the above-mentioned highly integrated effect of {100} <011> orientation cannot be sufficiently obtained.
It is well known that such thermal expansion / contraction behavior also depends on the heating rate, but in the present invention, it is determined from the thermal expansion / contraction behavior obtained when the heating rate is 2 ° C./s.
Since the effect of the present invention is more pronounced as the amount of γ phase formed increases in the process of thermal history, the larger the change is, the more preferable. In the present invention, this is defined by the temperature difference between T1 and T2.
As will be described later, it is preferable that the maximum temperature reached for finish annealing is T1 or less from the viewpoint of improving the ratio of {100} <011> orientation to random intensity. As will be described later, it is necessary to set the maximum temperature reached for finish annealing within the range of 750 ° C. or higher and lower than 1000 ° C. in order to obtain the desired magnetic properties and fatigue strength. Considering these, T1 may be 750 ° C. or higher, and if it is 1000 ° C. or higher, when it is within the range of 750 ° C. or higher and lower than 1000 ° C. Since the strength ratio is also improved, the chemical composition of the mother steel sheet is preferably in the range of T1 of 1000 ° C. or higher.
Further, since T2 of the mother steel sheet is T2> T1, the lower limit is more than T1. The upper limit is not particularly limited, but as will be described later, it is preferable to set the slab heating temperature to T2 or higher from the viewpoint of improving the ratio of the intensity to the random intensity of the {100} <011> orientation, and as will be described later, hot rolling. Considering that the slab heating temperature is preferably 1200 ° C. or lower from the viewpoint of avoiding inadvertent coarsening of the structure, T2 is preferably 1200 ° C. or lower. In other words, the chemical composition of the steel sheet of the present invention preferably has a T2 of 1200 ° C. or lower.
Further, T1 and T2 have a preferable relationship in relation to the degree of integration of the {100} <011> orientation. Regarding the α-γ transformation, the effect of the present invention in which the degree of integration of the {100} <011> orientation is increased becomes more remarkable as the amount of γ phase formed increases in the process of thermal history, as will be described later. It can be specified by the temperature difference between T1 and T2. That is, the larger the temperature difference between T2 and T1, the larger the abundance of the γ phase, which is convenient for obtaining the effect of the invention, and the chemical composition of the steel sheet of the present invention is T2-T1 ≧ 10. Is preferable.

(Inevitable impurities)
In the electromagnetic steel sheet of the present invention, the steel sheet may further contain various elements (unavoidable impurities) that are inevitably mixed as long as the effects of the present invention are not impaired.

The content ratio of each element in the steel sheet can be measured by, for example, inductively coupled plasma mass spectrometry (ICP-MS method). Specifically, first, an electromagnetic steel sheet to be measured is prepared. A part of the electrical steel sheet is cut into pieces and weighed, and this is used as a measurement sample. The sample for measurement is dissolved in an acid to prepare an acid solution, the residue is collected from a filter paper and separately melted in an alkali or the like, and the melt is extracted with an acid to form a solution. By mixing the solution and the acid solution and diluting it if necessary, an ICP-MS measurement solution can be obtained.

<{100} <011> X-ray random intensity ratio>
In the present invention, the crystal orientation and the crystal plane are generally described with respect to the surface of the steel sheet, which is used to express the orientation of the crystal in the steel sheet and the crystal plane and texture to be measured. That is, the crystal orientation is the orientation perpendicular to the surface of the steel sheet, and the crystal plane is the plane parallel to the surface of the steel sheet. Further, the expression is made by applying the extinction rule in the X-ray measurement of the crystal plane due to the crystal structure of the body-centered cubic which is the α phase of Fe. For example, {100} is used for the crystal orientation, and {200} is used for the crystal plane and texture, but these represent information on the same crystal grains.
Further, in the present invention, the X-ray random intensity ratio means a ratio to the X-ray integrated intensity of a sample in which the accumulation state of the crystal orientation is random.
The electromagnetic steel sheet of the present invention can increase the X-ray random intensity ratio of {100} <011> to the plate surface (steel plate surface) to obtain a high magnetic flux density in the 45 ° direction with respect to the rolling direction. Since the X-ray random intensity ratio of {100} <011> to the plate surface (steel plate surface) is 50 or more at the plate thickness 1/2 thickness position of the steel plate , the magnetic flux is sufficiently high in the 45 ° direction with respect to the rolling direction. The density can be obtained, and it is preferably 60 or more. Further, the upper limit of the X-ray random intensity ratio is not particularly limited, but since the effect of increasing the magnetic flux density is saturated, an X-ray random intensity ratio of 200 or less is usually sufficient.
The X-ray random intensity ratio of the α-Fe phase of {100} <011> is based on the pole diagrams of {200}, {110}, {310}, and {211} of the α-Fe phase measured by X-ray diffraction. It can be obtained from the crystal orientation distribution function (ODF) that represents a three-dimensional texture calculated by the series expansion method.
The random intensity ratio is the X-ray intensity of the standard sample and the test material that do not accumulate in a specific orientation under the same conditions, and the X-ray intensity of the obtained test material is the X-ray intensity of the standard sample. It is the value divided by the intensity. At that time, the measurement surface is finished by chemical polishing or the like so as to be smooth.

The electromagnetic steel sheet of the present invention may further have an insulating film on the surface of the steel sheet.
In the present invention, the insulating film is not particularly limited, and can be appropriately selected and used from known ones according to the intended use, and may be either an organic film or an inorganic film. Examples of the organic film include polyamine resins, acrylic resins, acrylic styrene resins, alkyd resins, polyester resins, silicone resins, fluororesins, polyolefin resins, styrene resins, vinyl acetate resins, epoxy resins, phenol resins, urethane resins, and melamines. Examples include resin. Examples of the inorganic film include a phosphate film, an aluminum phosphate film, and an organic-inorganic composite film containing the above resin.
The thickness of the insulating film is not particularly limited, but the film thickness per side is preferably 0.05 μm or more and 2 μm or less.

The method for forming the insulating film is not particularly limited, but for example, a composition for forming an insulating film in which the above resin or an inorganic substance is dissolved in a solvent is prepared, and the composition for forming the insulating film is uniformly applied to the surface of the steel sheet by a known method. An insulating film can be formed by applying to.

The thickness of the electromagnetic steel sheet of the present invention may be appropriately adjusted according to the intended use and is not particularly limited, but is usually 0.10 mm or more and 0.50 mm or less, and 0.015 mm from the viewpoint of manufacturing. More preferably 0.50 mm or less. From the viewpoint of the balance between magnetic characteristics and productivity, 0.015 mm or more and 0.35 mm or less is preferable.

The electrical steel sheet of the present invention is particularly suitable for applications in which it is punched into an arbitrary shape. For example, servo motors and stepping motors used in electrical equipment, compressors in electrical equipment, motors used in industrial applications, electric vehicles, hybrid cars, drive motors for trains, generators and iron cores used in various applications, chokes. Any of conventionally known applications in which an electromagnetic steel plate is used, such as a coil, a reactor, and a current sensor, can be suitably applied.
Above all, in the present invention, it can be suitably used for a rotor motor core and a stator motor core, which will be described later.
Further, in the electromagnetic steel sheet of the present invention, the effect of improving the fatigue strength of the electrical steel sheet can be obtained by making the precipitates coarse and low in number and making the average crystal grain size finer to 60 μm or more and 80 μm or less.

[Manufacturing method of electrical steel sheet]
The method for manufacturing an electromagnetic steel sheet according to the present invention is as follows.
Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0% by mass or less, and one kind selected from Ca, Mg, Ce, Ti, Ba, and Be. The above elements are contained in a total amount of 0.0001% by mass or more and 0.1% by mass or less, Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is less than 0.002% by mass. A hot rolling step in which an ingot containing Fe as a main component is used as a hot-rolled plate, a step of pickling the hot-rolled plate, a cold rolling step in which the hot-rolled plate is used as a cold-rolled plate, and the cold-rolled plate. Has a finishing annealing process and
The heating conditions of the finish annealing step are a heating rate of 5 ° C./s or more, a maximum ultimate temperature of 750 ° C. or more and less than 1000 ° C., and a holding time of 750 ° C. or more for 20 seconds or more and 150 seconds or less.

In the method for producing electrical steel sheets of the present invention, an ingot containing a specific amount of Mn is used, and in the finishing annealing step, average crystal grains are heat-treated under conditions of a higher heating rate than the conventional one and a slightly lower temperature than the conventional one. It is possible to manufacture an electromagnetic steel sheet having a diameter of 60 μm or more and 80 μm or less, and it is possible to obtain an electromagnetic steel sheet having excellent fatigue strength, low iron loss, and suppressed decrease in magnetic flux density during strain removing annealing.

The manufacturing process of the electromagnetic steel sheet of the present invention can be carried out by using the processes and equipment applied to general electromagnetic steel sheets.
For example, steel melted to a predetermined composition in a converter or electric furnace is secondarily refined in a degassing facility to form a steel slab by continuous casting or ingot rolling after ingot forming, and then hot rolling. , Hot-rolled sheet annealing, pickling, cold or warm rolling, finish annealing and insulating coating coating baking.

Here, in order to obtain a desired steel structure, it is necessary to control the production conditions as described below.
First, in casting, in order to avoid miniaturization of the oxide and form an oxide having a form suitable for the present invention, the cooling rate of the slab surface at which solidification has started is set to 0. It is preferably 1 ° C./s or more and 30 ° C./s or less. If the cooling rate is less than 0.1 ° C / s, the productivity is poor. Above 30 ° C./s, the oxide becomes fine, and it becomes difficult to form an oxide of an appropriate size and number density having the effect of the present invention.
First, during hot rolling, the slab heating temperature is set to 1200 ° C. or lower to avoid inadvertent coarsening of the pre-rolled structure. A steel sheet containing a high concentration of Si, such as the steel of the present invention, may become an α single-phase steel without α-γ transformation with respect to thermal history. In such a single-phase steel, if the steel has a transformation, the structure tends to be coarsened in a thermal history of about hot rolling such that the structure becomes finer due to the transformation. When the structure before hot rolling becomes coarse, a coarse processed structure (flat structure) remains after hot rolling, and rough skin called rigging or roping occurs on the surface of the steel sheet after cold rolling. The lower limit is not particularly limited, but it is appropriate to set the temperature to 1000 ° C. or higher in order to carry out rolling without impairing productivity in a general hot rolling facility. The preferred range is 1180 ° C. or lower, more preferably 1100 ° C. or lower.

Further, if necessary, hot-rolled sheet annealing is carried out. As the conditions, known conditions may be applied.
Hereinafter, the reasons for limitation in the manufacturing process (so-called one-time cold rolling method) of non-oriented electrical steel sheets to be cold-rolled and finish-annealed will be described.

Next, cold or warm rolling is performed, and the rolling reduction at this time is preferably 83% or more. This is because if the reduction rate is less than 83%, it becomes difficult to properly control the state of the crystal orientation that can avoid the deterioration of the magnetic characteristics due to the grain growth, which is a feature of the present invention.

Next, finish annealing is performed. The annealing conditions at this time are an average heating rate from 400 ° C. to 750 ° C.: 5 ° C./s or higher, a maximum temperature reached: 750 ° C. or higher and lower than 1000 ° C., and a holding time at 750 ° C. or higher. : 20 seconds or more and 150 seconds or less.
What is important in the above heat treatment conditions is the heating rate in annealing in which recrystallization is initiated after cold rolling. In order to obtain the effect of the present invention, the average heating rate from 400 ° C. to 750 ° C. should be 5 ° C./s or more. This can be said to be the basic mechanism for obtaining the above-mentioned effect of the present invention. When grain growth is subsequently performed by performing additional heat treatment by slow heating, grain growth is avoided, which leads to deterioration of magnetic properties. This is to obtain a crystal orientation that leads to an effect of avoiding deterioration of magnetic characteristics due to the above. If this heating is slow heating, it becomes difficult to obtain the effect of the present invention. It is preferably 20 ° C./s or higher, more preferably 100 ° C./s or higher, and even more preferably 400 ° C./s or higher.
Although it depends on the steel composition and hot rolling conditions, the maximum temperature reached and the holding time at 750 ° C. or higher are the targets for obtaining an appropriate crystal grain size. If the maximum temperature reached is less than 750 ° C. or the holding time at 750 ° C. or higher is less than 20 seconds, the crystal grain growth is insufficient and it becomes difficult to obtain magnetic characteristics, particularly sufficient iron loss. When the maximum temperature reached is 1000 ° C. or higher, it becomes difficult to control the crystal grain size within an appropriate range (80 μm or less), and sufficient fatigue strength cannot be obtained. Further, if the holding time at 750 ° C. or higher is more than 150 seconds, the crystal grain growth becomes excessive, and then the effect of avoiding the deterioration of the magnetic characteristics when the grain growth is performed by performing additional heat treatment by slow heating can be obtained. Not only is it difficult to retain the crystal orientation, but it is also difficult to maintain the high strength characteristic of the steel sheet of the present invention.

The case where the so-called one-time cold-rolling method, in which the final plate thickness is obtained by one warm or cold rolling after hot-rolled sheet annealing, has been described above, but the warm or cold rolling is sandwiched between intermediate annealing. It is also effective when applying the so-called double cold rolling method, which is applied twice.
The double cold rolling method is disadvantageous in terms of productivity compared to the single cold rolling method, but the strength of the material is high and the single rolling method exceeds the capacity of the rolling mill, or the magnetic properties are further increased. This is a suitable method for improvement.

After the finish annealing described above, it is advantageous to apply an insulating coating to the surface of the steel sheet in order to reduce iron loss. At this time, in order to ensure good punching property, an organic coating containing a resin is desirable, while when weldability is important, it is desirable to apply a semi-organic or inorganic coating.

Further, when manufacturing an electromagnetic steel sheet in which the ratio of random strength to random strength in the {100} <011> orientation at the position where the thickness of the steel sheet is 1/2 is 50 or more, for example, the following manufacturing method can be adopted.

That is, when an ingot having a chemical composition satisfying the α-γ transformation system is used, the method for producing an electromagnetic steel sheet according to the present invention is:
It is an α-γ transformation system, Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0% or less by mass, and Ca, Mg, Ce, Ti, Ba, And Be contains one or more elements selected from Be in total of 0.0001% by mass or more and 0.1% by mass or less, Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is 0. A hot rolling step of using an ingot containing Fe as a main component as a hot-rolled plate, a step of pickling the hot-rolled plate, and a cold-rolling step of using the hot-rolled plate as a cold-rolled plate, which is less than .002% by mass. It has a rolling process and a finishing annealing process for the cold-rolled plate.
The heating conditions of the finishing annealing step are a heating rate of 5 ° C./s or more, a maximum ultimate temperature of 750 ° C. or more and less than 1000 ° C., and a holding time of the ingot at T1 or less and 750 ° C. or more for 45 seconds or more and 150 seconds or less. It is characterized by that.

Hereinafter, when an ingot having a chemical composition satisfying the α-γ transformation system is used, a preferable method for setting the ratio of the intensity to the random intensity of the {100} <011> orientation to 50 or more will be described. The process conditions not described below may be in accordance with the above-mentioned production method not limited to the α-γ transformation system.

(Hot rolling process)
The slab to be subjected to hot rolling has a thickness of 50 mm or more cast by, for example, a known method, and after heating, a hot-rolled plate is obtained by rough rolling and finish rolling.
When an ingot having a chemical composition satisfying the α-γ transformation system is used in the production method of the present invention, the slab heating temperature is preferably T2 or higher. When using an ingot having a chemical composition that satisfies the α-γ transformation system, it is considered that transformation during hot rolling is one of the points. When the slab heating temperature is less than T2, the amount of structure that transforms from the austenite phase to the ferrite phase during hot rolling decreases, and the strength against randomness in the {100} <011> orientation after cold rolling and finish annealing. The ratio cannot be high enough. The reason for this is not clear, but it is considered that the fineness of the structure and the change in crystal orientation due to transformation during hot rolling, which are peculiar to the high Mn steel targeted by the present invention, have an effect.
Further, in order to avoid inadvertent coarsening of the pre-rolled structure, the slab heating temperature is preferably 1200 ° C. or lower, not limited to the ingot having the above-mentioned α-γ transformation system composition. The same is true.

When an ingot having a chemical composition satisfying the α-γ transformation system is used, in hot rolling, in order to suppress recrystallization during rolling, it is preferable to roll in a ferrite region at a rolling temperature of less than T1. For this purpose, the finish temperature (finish rolling end temperature) may be less than T1, but if the finish rolling start temperature is less than T1, all stages of finish rolling can be carried out in a temperature range of less than T1. It is preferable.
The above temperature is more preferably T1-50 ° C. or lower.

Further, when an ingot having a chemical composition satisfying the α-γ transformation system is used, since a steel sheet containing 2.5% by mass or more of Mn is used, the transfer rate of the rearrangement is extremely slow, and hot rolling is performed. In the finish rolling in the process, the austenite phase is maintained as it is processed even if the finish temperature exceeds T1 of the hot-rolled sheet. Therefore, after the finish rolling is completed, a cooling step of cooling to 250 ° C. or lower at a cooling rate of 200 ° C./sec or higher is provided within 3 seconds to transform the processed austenite into ferrite, thereby rolling in the ferrite region. It is possible to obtain the same effect. Of course, if the above cooling is applied with the finishing temperature set to less than T1, it is possible to obtain a hot-rolled steel sheet in which recrystallization of the processed ferrite phase is further suppressed, which is preferable.

After that, the steel plate is wound around the coil. In order to obtain the effect of the present invention that the ratio of {100} <011> orientation to random strength is 50 or more, recrystallization of the hot-rolled steel sheet should be avoided, and a low winding temperature is preferable. However, since the steel sheet of the present invention contains a large amount of Mn as described above and the progress of recrystallization is slow, 650 ° C. or lower is sufficient.

The production method using an ingot having a chemical composition satisfying the α-γ transformation system of the present invention is not limited, and it is obtained by the hot rolling step of the production method using an ingot having a chemical composition satisfying the α-γ transformation system. Although the hot-rolled plate to be produced is not limited, the hot-rolled plate after the hot-rolling step is preferable in order to obtain the effect of making the ratio of random strength to random strength of {100} <011> orientation 50 or more after cold-rolling annealing. The features appearing in are described in (1) to (5) below.

(1) Dislocation Density of Surface Layer of Hot Rolled Plate The above hot rolled plate preferably has a feature that the dislocation density of the surface layer is high. It is considered that the strain accumulated here effectively acts on the accumulation of the {100} <011> orientation after cold rolling annealing. The dislocation density is 2 × 1015 / m ² or more. When the dislocation density is ^{less than 2 × 1015 / m 2} and the strain is not sufficient, the cold rolling reduction ratio is set to, for example, 97% or more in order to sufficiently promote the development of the {100} <011> orientation after cold rolling annealing. There is also a need to increase the production efficiency, which is disadvantageous in terms of manufacturing efficiency. Here, the surface layer of the hot-rolled plate is at an arbitrary position of 20 μm or more and 1/4 t or less from the outermost surface. The dislocation density can be measured by the etch pit method or observation with a transmission electron microscope.
Further, it is preferable that the following characteristics appear in association with the increase in dislocation density.

(2) Vickers hardness of the surface layer of the hot-rolled plate The above-mentioned hot-rolled plate preferably has a feature that the Vickers hardness of the surface layer is high. Its hardness is 200 HV or more, and even 230 HV or more. In a situation where the hardness is low, recrystallization after hot rolling occurs excessively, the strain is released, and it can be judged that the above-mentioned dislocation density is lowered.

(3) Crystal grain size of the surface layer of the hot-rolled plate The crystal grains of the surface layer of the hot-rolled plate are preferably fine when they have a recrystallized structure. In a situation where the average crystal grain size is coarse, recrystallization after hot rolling occurs excessively, strain is released, and it can be judged that the above-mentioned dislocation density is lowered. The average particle size is, for example, 30 μm or less, preferably 25 μm or less. The average crystal grain size can be determined by the line segment method.

(4) Recrystallization rate of the hot-rolled plate Further, it is preferable that the hot-rolled plate has a characteristic that the crystal structure is not completely recrystallized. It can be judged that the recrystallization of the hot-rolled plate leads to the release of strain and the above-mentioned dislocation density is lowered. The recrystallization rate of the hot-rolled sheet represented by the following formula (1) is, for example, 90% or less, further 50% or less, and 0 (zero)% completely unrecrystallized structure (completely processed structure). The structure is convenient from the viewpoint of increasing the dislocation density. In the present invention, the processed structure is recognized as a fibrous structure that is not a crystal grain, as shown in the example of FIG.
Here, the recrystallization rate is obtained from an arbitrary cross section perpendicular to the rolled surface of the hot-rolled plate. The observation field of view shall be a region of at least the entire plate thickness x length of 5 mm. A plurality of observation fields may be used so that the total is the total plate thickness × length 5 mm or more.
Recrystallization rate (%) = (total area of recrystallized grains) ÷ (area of the entire observation field) x 100
... (Equation 1)

Further, in the hot-rolled plate, if the crystal grain size of the (3) hot-rolled plate surface layer and the recrystallization rate of the (4) hot-rolled plate have the following relationship, {100} after cold-rolling annealing. <011> Preferable due to the development of orientation.
When the recrystallization rate is more than 80% and 100% or less, the particle size of the recrystallized grains is preferably 15 μm or less.
When the recrystallization rate is more than 50% and 80% or less, the particle size of the recrystallized grains is preferably 20 μm or less.
When the recrystallization rate is more than 20% and 50% or less, the particle size of the recrystallized grains is preferably 25 μm or less.
When the recrystallization rate is 20% or less, the particle size of the recrystallized grains is preferably 40 μm or less, more preferably 30 μm or less.

As the manufacturing conditions that satisfy the above-mentioned properties of the hot-rolled plate, for example, the following points may be noted and appropriately adjusted.
For example, finish rolling is performed in a ferrite region where recrystallization is unlikely to occur. When finish rolling is performed in a temperature range that causes phase transformation, recrystallization of the austenite phase after hot rolling is suppressed by quenching at a cooling rate of 200 ° C./sec or more within 3 seconds immediately after rolling. Then, the processed austenite can be transformed into ferrite to accumulate strain.

In the present invention, since a steel sheet containing 2.5% by mass or more of Mn is used, the moving speed of the grain boundaries is extremely slow, and in the finish rolling in the hot rolling process, the finishing temperature is set to that of the hot rolled sheet. Even if it exceeds T1, the processed austenite is maintained. However, if the finishing temperature is above T1 of the hot-rolled plate, then a cooling step of cooling the hot-rolled plate over T1 to 250 ° C. or less at a cooling rate of 200 ° C./sec or more within 3 seconds is performed. Need to be provided. By providing the cooling step, the iron loss of the obtained electromagnetic steel sheet can be reduced. By cooling within 3 seconds, recrystallization of austenite can be suppressed and the strain of the hot-rolled plate can be maintained.

Further, in the finish rolling in the hot rolling step, the finishing temperature is T1-50 ° C. or lower of the hot-rolled sheet, so that the iron loss of the obtained electromagnetic steel sheet can be reduced even if the cooling step is not provided. Can be done.

(5) Assembled structure of hot-rolled sheet The texture of the steel plate surface layer of the hot-rolled sheet after finish rolling has an X-ray random intensity ratio of {110} <223> of 3 or more, and {332} <243. > Is 0.5 or less, {112} <111> is 2 or more, {223} <122> is 1 or less, and {100} <011 at the 1 / 2t position of the hot-rolled sheet after finish rolling. > Is preferably smaller than the X-ray random intensity ratio of {311} <011>. Strain is accumulated in the hot-rolled sheet in which {332} <243> is 0.5 or less and {223} <122> is 1 or less, and {100} <011> is sufficient after cold rolling and annealing. Therefore, it is easy to manufacture the electromagnetic steel sheet according to the present invention.

(Hot rolled plate annealing process)
In the present invention, in order to produce an electromagnetic steel sheet having an X-ray random intensity ratio of {100} <011> of 50 or more after cold rolling annealing, annealing is performed between the hot rolling step and the cold rolling step described later. It is preferable not to have a step. That is, it is possible to suppress the recrystallization of the hot-rolled plate and strongly express the above-mentioned characteristics (1) to (5) by not performing the conventional hot-rolled plate annealing.

(Cold rolling process)
The cold rolling step is not particularly limited, and the cold rolling step in the conventionally known method for manufacturing electrical steel sheets can be appropriately adopted. For example, any rolling method such as a reverse rolling method or a tandem rolling method may be used. In the present invention, setting the cold reduction ratio to 88% or more increases the {100} <011> component of the obtained electrical steel sheet, has a high magnetic flux density, low iron loss in a high frequency region, and further high strength. It is preferable from the viewpoint that an electromagnetic steel sheet can be obtained, and the total reduction ratio is more preferably 90% or more.

(Finishing annealing process)
The finish annealing step performed in the cold rolling step is not particularly limited, but from the viewpoint of maintaining the {100} <011> component in the steel sheet, the average heating rate from 400 ° C. to 750 ° C.: 5 ° C./s or more. Maximum reached temperature: 750 ° C. or higher and lower than 1000 ° C., and T1 or lower, holding time at 750 ° C. or higher: 20 seconds or longer and 150 seconds or lower.
As described above, when the maximum temperature at which the finish annealing temperature is reached is less than 750 ° C., recrystallization and grain growth are slow, and the time required to obtain low iron loss becomes long. When the maximum temperature reached is 1000 ° C. or higher, it becomes difficult to control the crystal grain size within an appropriate range (80 μm or less), and sufficient fatigue strength cannot be obtained.
In addition, in the α-γ transformation type steel sheet, when T1 is exceeded, α-γ transformation occurs and the texture is randomized, so that the accumulation in the {100} <011> orientation is reduced. Further, setting the maximum temperature reached to T1 or less is also advantageous for the residual crystal orientation that can obtain the effect of avoiding deterioration of magnetic properties when grain growth is performed by performing additional heat treatment by slow heating thereafter. ..
Therefore, when T1 of the mother steel sheet is 1000 ° C. or higher, if the maximum temperature reached is 750 ° C. or higher and lower than 1000 ° C., the X-ray random intensity ratio of {100} <011> is inevitably 50 or higher. However, when T1 of the mother steel sheet is less than 1000 ° C., if the maximum temperature reached is 750 ° C. or higher and T1 or lower, the X-ray random intensity ratio of {100} <011> is 50 or higher. It is preferable for this.
According to the above manufacturing method, an electromagnetic steel sheet having an average crystal grain size of 60 μm or more and 80 μm or less and a ratio of {100} <011> orientation to random strength at a position of 1/2 thickness of the steel sheet is suitable. Can be manufactured in.

According to the above-mentioned method for manufacturing an electromagnetic steel sheet, an ingot containing a specific amount of Mn is used, and in the finishing annealing step, the steel sheet is heat-treated under conditions of a higher heating rate than the conventional one and a slightly lower temperature than the conventional one. Electromagnetic steel with a {100} <011> orientation to random strength ratio of 50 or more at the plate thickness 1/2 thickness position, excellent fatigue strength, low iron loss, and suppression of decrease in magnetic flux density during strain removal annealing. A steel plate can be obtained.

[Manufacturing method of motor core]
The method for manufacturing a motor core according to the present invention is a method for manufacturing a motor core having a rotor motor core described later and a stator motor core described later.
The steel plate blank of the motor core for the rotor and the steel plate blank of the motor core for the stator are punched from the electromagnetic steel plate according to the present invention.

The method for manufacturing a motor core of the present invention is excellent in productivity because a steel plate blank of a motor core for a rotor and a steel plate blank of a motor core for a stator can be punched out from the same electromagnetic steel plate.

A method for manufacturing a motor core according to the present invention will be described with reference to FIG. FIG. 1 is a schematic schematic process diagram showing an example of a method for manufacturing a motor core.
(A) in FIG. 1 is a step of punching a steel plate blank 2'of a motor core for a rotor and a steel plate blank 3'of a motor core for a stator from one electromagnetic steel plate 1.
The punching method is not particularly limited, and any conventionally known method may be adopted.

By laminating the punched steel sheet blanks 2 for the rotor, a motor core for the rotor can be obtained.
That is, the rotor motor core of the present invention is characterized in that the electromagnetic steel sheets according to the present invention are laminated.
Further, the method for manufacturing a motor core for a rotor of the present invention includes a step (I) of obtaining a steel sheet blank by punching the electromagnetic steel sheet according to the present invention.
It has a step (II) of laminating the steel sheet blanks.

The method of laminating the steel plate blanks 2 of the rotor motor core is not particularly limited, and any conventionally known method may be adopted. Further, the laminated body of the steel plate blank 2 may have an adhesive layer or the like formed by applying a known adhesive or the like when laminating the steel plate blank 2.

Since the motor core for a rotor of the present invention is manufactured by using the electromagnetic steel plate according to the present invention, it has excellent fatigue strength, low iron loss, and high magnetic flux density.
In the method for manufacturing a motor core for a rotor of the present invention, conventionally known methods can be appropriately adopted as the punching method and the laminating method. From the viewpoint of high fatigue strength, it is preferable that the rotor motor core is not strain-removed and annealed.

Further, a specific stator motor core can be obtained by laminating the punched steel plate blank 3 of the stator motor core under specific conditions after laminating, or by laminating after heat treatment under specific conditions.

That is, the method for manufacturing a motor core for a stator according to the present invention includes a step (I') of obtaining a steel sheet blank by punching the electromagnetic steel sheet according to the present invention.
It has a step (II') of laminating the steel sheet blanks.
After the step (I') and before or after the step (II'), the steel sheet blank is heated at a heating rate of 100 ° C./h or less and a maximum reaching temperature of 750 ° C. to 850 ° C., 750 ° C. or higher. It is characterized by having a step (III') of making the average crystal grain size of the steel sheet more than 80 μm and 150 μm or less by performing the heat treatment under the condition that the holding time of the steel sheet is 0.5 hours or more and 100 hours or less.

In the method for manufacturing a motor core for a stator of the present invention, the average crystal grain size of the electromagnetic steel sheet according to the present invention is changed according to the above heat treatment conditions. What is important in the above heat treatment conditions is to slow down the heating rate to 100 ° C./h or less, unlike the heat treatment conditions in the finish annealing step in the method for manufacturing electrical steel sheets of the present invention. This is to obtain the preferential growth property of the crystal orientation which leads to the effect of avoiding the deterioration of the magnetic properties due to the grain growth, which can be said to be the basic mechanism for obtaining the above-mentioned effect of the present invention. If this heating is rapidly changed, the preferential growth property in a specific preferable direction is lost, and it becomes difficult to obtain the effect of the present invention. It is preferably 80 ° C./h or less, more preferably 60 ° C./s or less, still more preferably 40 ° C./s or less.
Although it depends on the steel composition and hot rolling conditions, the maximum temperature reached and the holding time at 750 ° C. or higher are the targets for obtaining an appropriate crystal grain size. If the maximum temperature reached is less than 750 ° C. or the holding time at 750 ° C. or higher is less than 0.5 hours, crystal grain growth hardly occurs, the effect of the invention cannot be sufficiently obtained, and the magnetism required as a motor core for a stator is not obtained. It becomes difficult to obtain characteristics, especially iron loss. If the maximum temperature reached exceeds 850 ° C. or the holding time at 750 ° C. or higher exceeds 100 hours, the crystal grain growth becomes excessive, the magnetic flux density decreases, and the iron loss also increases.
In the method for manufacturing a motor core for a stator of the present invention, a steel sheet blank is held at a heating rate of 100 ° C./h or less, a maximum temperature reached: 750 ° C. to 850 ° C., and a holding time of 750 ° C. or higher: 0.5 hours or more and 100 hours. By performing the following heat treatment, the average crystal grain size can be set to more than 80 μm and 150 μm or less without changing the crystal orientation.
In the method for manufacturing a motor core for a stator of the present invention, conventionally known methods can be appropriately adopted as the punching method and the laminating method. From the viewpoint of reducing iron loss, the stator motor core is subjected to strain removing annealing (step (III')) after the step (I') and before or after the step (II'). Since the average crystal grain size is more than 80 μm and 150 μm or less by the above step (III'), low iron loss can be achieved, while the electromagnetic steel sheet according to the present invention is used, so that the step (III') is used. A high magnetic flux density is maintained even after heating, and an excellent motor core for a stator can be obtained.

The stator motor core according to the present invention contains Si in an amount of 2.0% by mass or more and 4.5% by mass or less, Mn in an amount of 2.5% by mass or more and 5.0% by mass or less, and further Ca, Mg, Ce, Ti, Ba. , And one or more elements selected from Be in total containing 0.0001% by mass or more and 0.1% by mass or less, Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is. It is a steel plate containing less than 0.002% by mass and containing Fe as a main component, and is characterized in that electromagnetic steel plates having an average crystal grain size of more than 80 μm and 150 μm or less are laminated.

Since the motor core for a stator of the present invention is manufactured by the method for manufacturing a motor core for a stator according to the present invention using the electromagnetic steel plate according to the present invention, it has a low iron loss and a high magnetic flux density.

Further, in the stator motor core of the present invention, the steel plate (that is, the electromagnetic steel plate after strain removal and annealing as a material) has an oxide, and the average composition of the oxide is 15% by mass or more and 70% by mass of Si. Hereinafter, it is preferable that Mn is contained in an amount of 20% by mass or more and 60% by mass or less, the average diameter of the oxide is more preferably 250 nm or more, and the number density of the oxide in the steel plate is 2.0 ×. More preferably, it is 10 ^{4 to} 1.2 × 10 ⁵ pieces / mm ^2. According to such a motor core for a stator, a higher magnetic flux density can be achieved. In such a preferable motor core for a stator, the electromagnetic steel plate of the present invention (that is, the steel plate before strain relief annealing) has an oxide, and the average composition of the oxide is 15% by mass or more and 70% by mass or less of Si. , those containing Mn 20 wt% to 60 wt% or less, further, the an average diameter of the oxide is 250nm or more, further, the number density of 2.0 × ¹⁰ 4 to 1 in the steel sheet of the oxide It can be manufactured by selecting and using a product having a size of .2 × 10 ⁵ pieces / mm ^2.

The conditions in the examples described below are one-condition examples adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to this one-condition example. The present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

(Example: Manufacturing of electrical steel sheet)
Ingots adjusted to the composition shown in the steel grades A to L in Table 1 were cast in a vacuum melting furnace. Each of these ingots was made into an electromagnetic steel sheet based on the manufacturing conditions in Table 2. Specifically, the slab heated to 1150 ° C. is hot-rolled at the finish rolling temperature shown in Table 2, the time from the final pass of the hot-rolling to the start of cooling is set to 3 seconds or less, and the cooling rate is 200. The mixture was cooled to 250 ° C. or lower at ° C./sec or higher and wound at 630 ° C. to obtain hot-rolled plates having a thickness of 2.3 to 3.0 mm, respectively, as shown in Table 2.
The hot-rolled plate thus obtained was cold-rolled without annealing to obtain a cold-rolled plate having a thickness of 0.2 to 0.3 mm. Next, finish annealing was performed in a nitrogen atmosphere at the temperature and holding time shown in Table 2.

The evaluation characteristics in the examples were determined by the following method.
The unrecrystallized ratio and the unrecrystallized region diameter were determined by polishing and etching the rolling direction cross section (ND-RD cross section) of the steel sheet and observing EBSD (Electron Backscatter Diffraction Patterns).
Fatigue strength was evaluated by a tensile fatigue test based on the test method described in JIS Z2273.
_{As for the magnetic characteristics, the magnetic flux density B 50} for a magnetization force of 5000 A / m was determined using SST (Single Sheet Tester) in accordance with the magnetic steel veneer single plate magnetic characteristics test method described in JIS C 2556. At this time, the measurement frequency is set to 50 Hz. The test piece for SST was taken in the direction of 45 ° with respect to the rolling direction.
The results are shown in Table 2-1 and 2-2, Table 3-1 and Table 3-2.

As shown in Table 1, in the steel types E, F, G, H, J, and L, Si is 2.0% by mass or more and 4.5% by mass or less, and Mn is 2.5% by mass or more and 5.0% by mass. Hereinafter, further, one or more elements selected from Ca, Mg, Ce, Ti, Ba, and Be are contained in a total of 0.0001% by mass or more and 0.1% by mass or less, and Al is 0.03% by mass. It does not satisfy the composition conditions of less than, C is less than 0.002% by mass, and S is less than 0.002% by mass (hereinafter, may be referred to as composition A).
Test No. 2 produced by the method shown in Table 2-1 using steel types E, F, G, H, J, and L as slabs. In the non-oriented electrical steel sheets 5, 6, 7, 8, 10, and 12, as shown in Table 3-1 the B50 was lowered by heating at 750 ° C. for 90 minutes, and the BB / BA was 0.950 or less. It became clear that it would be.
On the other hand, as shown in Table 1, the steel types A, B, C, D, I, and K satisfy the composition A.
Test No. 2 produced by the method shown in Table 2-1 using steel types A, B, C, D, I, and K as slabs. In the non-oriented electrical steel sheets 1, 2, 3, 4, 9, and 11, as shown in Table 3-1 the decrease in B50 was suppressed by heating at 750 ° C. for 90 minutes, and the BB / BA was 0.988. It became clear that the above was achieved.

Next, paying attention to the finish annealing step , even when a steel grade satisfying the composition A is used as the slab, the finish annealing temperature is less than 750 ° C. In 13 and 25, since the average crystal grain size could not be 60 μm or more, the iron loss was worse than that of other steel sheets having the same composition.
Further, even when a steel grade satisfying the composition A is used as a slab and the finishing annealing temperature is 850 ° C., the holding time at 850 ° C. is as short as 15 seconds. In No. 31, since the average crystal grain size could not be 60 μm or more, the iron loss was worsened as compared with other steel sheets having the same composition.
Similarly, even when a steel grade satisfying the composition A is used as the slab, the test No. 1 in which the finish annealing temperature is 1000 ° C. or higher. In 16 and 40, the average crystal grain size was 80 μm or more, and the fatigue characteristics were deteriorated as compared with other steel sheets having the same composition.
Further, even when a steel grade satisfying the composition A is used as a slab and the finishing annealing temperature is 850 ° C., the holding time at 850 ° C. is as long as 200 seconds. 34. Test No. with a slow temperature rise rate of 2 ° C / s. In 23 and 32, the average crystal grain size was 80 μm or more, and the fatigue characteristics were deteriorated as compared with other steel sheets having the same composition.
On the other hand, a steel grade satisfying the composition A is used as a slab, and the holding time at a heating rate of 5 ° C./s or more, a maximum reaching temperature of 750 ° C. or more and less than 1000 ° C., and a holding time of 750 ° C. or more is 45 seconds or more and 150 seconds or less. Test No. 1 which was finished and annealed under heating conditions (hereinafter, may be referred to as heating condition A). At 14, 15, 17-22, 24, 26-30, 33, 35-39, 41 and 42, the average crystal grain size was 60-80 μm, and iron loss, fatigue characteristics, and BB / BA were 0.95 or more. It was excellent.

When a steel grade satisfying the composition A is used as the slab and the heating condition A is satisfied, if the cold speed of continuous casting is in the range of 0.1 to 30 ° C./s, the composition of the oxide in the steel sheet is Si. It is possible to contain Mn in an amount of 15% by mass or more and 70% by mass or less and Mn in an amount of 20% by mass or more and 60% by mass or less. Therefore, it has been clarified that BB / BA is 0.97 or more.
Further, when a steel grade satisfying the composition A is used as the slab and the heating condition A is satisfied, the average diameter of oxides in the steel sheet is average when the cold speed of continuous casting is in the range of 0.2 to 20 ° C./s. It has been clarified that the BB / BA is 0.98 or more because it is possible to set the value to 250 nm or more.

1 Electromagnetic steel sheet 2, 2'Steel steel sheet blank for rotor 3, 3'Steel steel sheet blank for stator

Claims (14)

Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0 % by mass or less, and one kind selected from Ca, Mg, Ce, Ti, Ba, and Be. The total of the above elements is 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, S is less than 0.002% by mass , the balance Fe and unavoidable. A steel plate made of impurities
The average crystal grain size is 60 μm or more and 80 μm or less .
The steel sheet has an oxide containing Si and Mn, the average diameter of the oxide is 112 nm or more, and the number density of the oxide contained in the steel sheet is 0.3 × 10 ^{4 to} 6.6 ×. Electromagnetic steel sheet with 10 ⁵ pieces / mm ^2. The electromagnetic steel sheet according to claim 1, wherein the average composition of the oxide contains Si in an amount of 15% by mass or more and 70% by mass or less and Mn in an amount of 20% by mass or more and 60% by mass or less. The electromagnetic steel sheet according to claim 2, wherein the average diameter of the oxide is 250 nm or more. The electromagnetic steel sheet according to claim 2 or 3, wherein the number density of the oxide contained in the steel sheet is 2.0 × 10 ^{4 to} 1.2 × 10 ⁵ pieces / mm ^2. After performing the magnetic flux density before performing the heat treatment under the conditions of a heating rate of 100 ° C./h or less, a maximum reaching temperature of 750 ° C. to 850 ° C., and a holding time of 750 ° C. or more for 0.5 hours or more and 100 hours or less. When the magnetic flux density of
BB / BA ≧ 0.98
The electromagnetic steel sheet according to any one of claims 1 to 4, wherein the electromagnetic steel sheet is characterized by the above. The steel sheet is an α-γ transformation system.
The electromagnetic steel sheet according to any one of claims 1 to 5, wherein the ratio of the random strength to the {100} <011> orientation at the position of 1/2 thickness of the steel sheet is 50 or more. The method for manufacturing an electromagnetic steel sheet according to any one of claims 1 to 6.
Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0 % by mass or less, and one kind selected from Ca, Mg, Ce, Ti, Ba, and Be. The total of the above elements is 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, S is less than 0.002% by mass , the balance Fe and unavoidable. A hot rolling step in which an ingot made of impurities is used as a hot-rolled plate, a step of pickling the hot-rolled plate, a cold rolling step in which the hot-rolled plate is used as a cold-rolled plate, and a finish annealing of the cold-rolled plate. Has a process and
The heating conditions of the finish annealing step are an average heating rate of 5 ° C./s or more from 400 ° C. to 750 ° C., a maximum reaching temperature of 750 ° C. or more and less than 1000 ° C., and a holding time of 45 seconds or more and 150 seconds or less at 750 ° C. or more. There is a manufacturing method of electromagnetic steel plate. The method for manufacturing an electromagnetic steel sheet according to claim 6.
It is an α-γ transformation system, with Si of 2.0% by mass or more and 4.5% by mass or less, Mn of 2.5% by mass or more and 5.0 % by mass or less, and Ca, Mg, Ce, Ti, Ba, In total, one or more elements selected from Be and Be are 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, and S is 0.002. A hot rolling step of using an ingot consisting of less than mass% of Fe and unavoidable impurities as a hot-rolled plate, a step of pickling the hot-rolled plate, and a cold rolling step of using the hot-rolled plate as a cold-rolled plate. The cold-rolled plate has a finishing annealing step.
The heating conditions of the finish annealing step are an average heating rate of 5 ° C./s or more from 400 ° C. to 750 ° C., a maximum ultimate temperature of 750 ° C. or more and less than 1000 ° C., and heat when the ingot is heated from the α phase single phase. A method for manufacturing an electromagnetic steel plate, which has a holding time of 20 seconds or more and 150 seconds or less at a temperature of T1 or less and 750 ° C. or more, which is defined as a turning point deviating from the linear expansion behavior in the expansion behavior in a direction in which the inclination becomes smaller. A motor core for a rotor, which is formed by laminating the electromagnetic steel sheets according to any one of claims 1 to 6. A step (I) of obtaining a steel sheet blank by punching the electromagnetic steel sheet according to any one of claims 1 to 6.
A method for manufacturing a motor core for a rotor, which comprises a step (II) of laminating the steel plate blanks. Si is 2.0% by mass or more and 4.5% by mass or less, Mn is 2.5% by mass or more and 5.0 % by mass or less, and one kind selected from Ca, Mg, Ce, Ti, Ba, and Be. The total of the above elements is 0.0001% by mass or more and 0.10 % by mass or less , Al is less than 0.03% by mass, C is less than 0.002% by mass, S is less than 0.002% by mass , the balance Fe and unavoidable. A steel plate made of impurities, the average crystal particle size is more than 80 μm and 150 μm or less, the steel plate has an oxide containing Si and Mn, and the average diameter of the oxide is 112 nm or more. the oxidation the number density contained in the electromagnetic steel sheets are laminated is 0.3 × ¹⁰ 4 ~6.6 × ^{10 5} cells / mm ^2, motor core stator. The motor core for a stator according to claim 11, wherein the average composition of the oxide contains Si in an amount of 15% by mass or more and 70% by mass or less and Mn in an amount of 20% by mass or more and 60% by mass or less. A step (I') of obtaining a steel sheet blank by punching the electromagnetic steel sheet according to any one of claims 1 to 6.
It has a step (II') of laminating the steel sheet blanks.
After the step (I') and before or after the step (II'), the steel sheet blank is heated at a heating rate of 100 ° C./h or less and a maximum reaching temperature of 750 ° C. to 850 ° C., 750 ° C. or higher. 11 or 12 according to claim 11, further comprising a step (III') of adjusting the average crystal grain size of the steel sheet to more than 80 μm and 150 μm or less by performing the heat treatment under the condition that the holding time of the steel sheet is 0.5 hours or more and 100 hours or less. Manufacturing method of motor core for stator. A method for manufacturing a motor core having the rotor motor core according to claim 9 and the stator motor core according to claim 11 or 12.
A method for manufacturing a motor core, wherein the steel plate blank of the motor core for a rotor and the steel plate blank of the motor core for a stator are punched from the same electromagnetic steel plate according to any one of claims 1 to 6.

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